Spool



FIG. 1 is a front perspective view of a spool, showing my new design;

FIG. 2 is a rear perspective view of my spool of FIG. 1;

FIG. 3 is a front view of my spool of FIG. 1; and,

FIG. 4 is a side view of my spool of FIG. 1, the opposite side view being the same. 

The ornamental design for a spool, as shown and described. 